I thought this worth talking about as I've been in discussions with a number of people recently around best practices for data types etc. The example in the discussion was the implementation of Descriptive Flex Views in Oracle E-Business Suite.
As a bit of background for those who may not be aware, some standard E-Business Suite tables contains a number of generic fields which a developer can utilize to hold their own custom fields. For example, here is a descriptive flexfield against the documents attachment table FND_ATTACHED_DOCUMENTS.
You can see I've created a new attribute against which I can hold some custom information. When I save and "freeze" that, I get a notification that the flexfield has been generated.